#include <iostream>
#include <string.h>
#include <string>
#include <cstdio>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>


int main()
{
    pid_t id = fork();
    if(id < 0)
    {
        printf("error: %d, errstring: %s\n",errno, strerror(errno));
        return errno;
    }
    else if(id == 0)
    {
        int cnt = 5;
        while(cnt)
        {
            printf("我是子进程, pid：%d\n ",getpid());
            cnt--;
            sleep(1);
        }

        exit(123);
    }
    else 
    {
       // sleep(6);
        //pid_t rid = wait(nullptr);
        //pid_t rid = waitpid(-1, nullptr, 0);
        //pid_t rid = waitpid(id, nullptr, 0);
        int status = 0;
        pid_t rid = waitpid(id, &status, 0);
        if(rid > 0)
        {
            if(WIFEXITED(status))
            {
            printf("wait sub process success, rid: %d ,status code : %d, exit signal:%d\n",rid, (status>>8)&0xFF, status&0x7F);
            }
            else 
            {
                printf("child process quit");
            }
        }
        else 
        {
            perror("waitpid");
        }
        while(true)
        {
            printf("我是父进程, pid: %d\n", getpid());
            sleep(1);
        }
    }

   // char *p = nullptr;
   // *p = 'a';
    return 0;
}
